Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$38.70	7.729%	$41.6911	$41.69	$41.70	$41.70
Purchase #2	$25.86	10.303%	$28.5244	$28.52	$28.50	$28.50
Purchase #3	$17.92	11.762%	$20.0278	$20.03	$20.05	$20.00
Purchase #4	$9.44	12.728%	$10.6415	$10.64	$10.65	$10.60
Purchase #5	$164.92	4.468%	$172.2886	$172.29	$172.30	$172.30
Purchase #6	$59.99	10.755%	$66.4419	$66.44	$66.45	$66.40
Purchase #7	$162.41	11.204%	$180.6064	$180.61	$180.60	$180.60
7 purchase totals =	$479.24		$520.2217	$520.22	$520.25	$520.10